1. Field of the Invention
This invention generally relates to the distribution of electrical power in a network, and more specifically to power distribution substations (commonly referred to as “unit substations”) adapted to receive electrical power at a first voltage and distribute power to a network at a different voltage.
2. Related Art
Electrical power control and distribution systems are commonplace in modern electrical distribution systems. A unit substation is a power distribution substation, which generally receives electrical power at a higher voltage, and distributes power to a network at a lower voltage, such as, for example, in a network used in a hospital or other facility. A unit substation typically consists of three physically and electrically connected components, comprising a primary protective or isolation device, a substation transformer, and secondary distribution equipment.
Several United States-recognized standards address design requirements for components of the power distribution substation industry. These standards include, for example, Circuit Breaker specifications, such as the National Electrical Manufacturers Association (NEMA) Standard SG-3, ANSI Standards C37.13, C37.16, C37.17, and Underwriter's Laboratories (UL) specifications UL 1066 and 489. These standards also include switchgear standards, such as, for example, NEMA Standard SG5, Canadian Standards Association (CSA), ANSI 37.20.1, C37.20.2, C37.20.3, C37.51, and UL Standard 1558 and 891. Each of the standards noted above are incorporated by reference herein for their teachings on power distribution equipment design.
One disadvantage of prior art unit substations is associated with the amount of floor space occupied by the substation. As noted above, one typical application of a unit substation is for use in a building, wherein the substation typically occupies a large area of floor space required by the substation footprint. The floor space occupied by unit substations can become burdensome to a building space planner or building owner.
Another disadvantage associated with unit substations is related to errors arising from substation installation “coordination” activities. Generally, there are at least three distribution substation components that must be carefully coordinated and installed correctly, otherwise errors result. For example, in the traditional distribution substation, the primary protective device is physically separated from the secondary distribution equipment by the substation transformer. The conduits and cables must fit precisely into poured concrete in a building floor, for example, which are custom-designed in accordance with the precise substation dimensions. The dimensional location of the primary conduit and cable, in relation to the secondary distribution equipment, is based upon the physical width dimensions of the substation transformer, which is located between the primary and secondary equipment. If the dimension of the substation transformer changes after the initial dimensions of the concrete slab have been established, the location of the primary conduit must be changed accordingly. This imposes severe cost and time constraints on the substation installation. The present invention overcomes this problem.
Therefore, there is a need for an improved power distribution substation that provides a reduced substation footprint, reduces the number of components required to operate each substation, and eases the installation tasks associated therewith, thereby reducing errors associated with coordination activities, such as, for example, the pouring of concrete, and the installation of support channels and conduits.
The improved unit substation overcomes the disadvantages noted above while reducing overall costs to the power distribution substation customer.